The generation of rotating movements or swirl in the cylinder intake charge of piston type internal combustion engines by inlet ports of various configurations has long been recognized in the engine art as a means of increasing turbulent flame speed, charge burn rate, combustion thermal efficiency and lean burn capability as well as having other advantages. Various forms of swirl generating inlet configurations have been proposed, among which are masked or shrouded valves, angled or directed ports, helical ports and directed ports with deflector walls or blades of various shapes.